Fix for CID 529870, where Coverity found an issue where `timespec.tv_sec`
is never greater than `UINT64_MAX / NSEC_PER_SEC` (18446744073).
This is naturally true when `time_t` is only 32-bit, which is actually
never the case for any Zephyr platform aside from `native_sim/native/32`.
When `time_t` is a signed 64-bit value, at some point in the future, but
maybe not in our lifetimes, `timespec.tv_sec` could exceed 18446744073,
since `INT64_MAX > UINT64_MAX / NSEC_PER_SEC`.
We should not see coverity issues errors like this in the future, once we
have a consistent `time_t` representation across all Zephyr platforms.
Signed-off-by: Chris Friedt <cfriedt@tenstorrent.com>
Additional entries for the sys_clock API, comprised of:
* sys_clock_gettime()
* sys_clock_settime()
* sys_clock_nanosleep()
along with the constants
* SYS_CLOCK_REALTIME
* SYS_CLOCK_MONOTONIC
* SYS_TIMER_ABSTIME
The primary motivation for this API is so that libc and other
libraries have a familiar-enough API to reach to when POSIX
is not available, since POSIX is optional in Zephyr.
By adding this API to lib/os, we also eliminate dependency cycles
between libc and posix, as lib/os is a mutual dependency.
Signed-off-by: Chris Friedt <cfriedt@tenstorrent.com>
